JP7394439B2 - Conductive multifilament, method for manufacturing conductive multifilament, woven or knitted fabric, and brush - Google Patents

Description

The present invention relates to a conductive multifilament with excellent conductivity and suppressed variations in conductivity, a method for manufacturing the conductive multifilament, and a woven or knitted fabric and a brush containing the conductive multifilament.

Fibers made of hydrophobic polymers such as polyester resins, polyamide resins, or polyolefin resins have many properties such as mechanical properties, chemical resistance, and weather resistance. Therefore, it is widely used for clothing and industrial materials. The surfaces of these fibers tend to generate static electricity due to friction when worn, for example, which can attract dust from the air, degrading the aesthetic appearance of the fiber surfaces, and causing electric shock to the human body, which can even cause discomfort. . Furthermore, when used in electronic equipment or precision equipment, the generation of static electricity can cause fatal failures or ignite flammable substances. Therefore, in order to solve these problems caused by static electricity, fibers imparted with conductivity are being considered.

As a method of imparting conductivity, for example, fibers in which conductive particles such as carbon black or metal powder are dispersed in a thermoplastic polymer are known (for example, Patent Document 1).

Japanese Patent Application Publication No. 2003-105623

Patent Document 1 proposes a multifilament that exhibits stable electrical resistance values with small variations in electrical resistance values between single fibers. However, when such multifilaments are used for clothing and industrial materials as mentioned above, fiber deformation occurs when used in environments with large temperature changes or when exposed to high temperature environments such as when using an iron. There is a problem in that it is difficult to obtain uniform conductivity in the length direction of the fibers.

The present invention solves the problems of the prior art as described above, and provides a conductive multifilament that has excellent conductivity and suppresses variations in conductivity even when used in environments with large temperature changes. is a technical issue.

As a result of intensive studies, the present inventors found that a conductive multifilament with a low dry heat shrinkage rate and suppressed yarn unevenness has excellent conductivity and suppresses variations in conductivity and variations in conductivity in high-temperature environments. The present invention was completed based on the discovery that uniform conductivity could be achieved by using the same method.

That is, the gist of the present invention is the following (1) to (7).
(1) A multifilament composed of single fibers made of polyamide resin containing conductive particles in a proportion of 15 to 35% by mass, characterized by simultaneously satisfying the following (I) to (V). Conductive multifilament.
(I) Dry heat shrinkage rate at 170°C is 3.0% or less (II) Electrical resistance value at 25°C and 170°C is 10 ¹² Ω/cm or less (III) Thread unevenness is 3.0% or less (IV) 25°C The CV value of the electrical resistance value in the longitudinal direction of the fiber at 170°C is 5.0% or less (V) The CV value of the electrical resistance value in the longitudinal direction of the fiber at 170°C is 5.5% or less (2) Fineness The conductive multifilament (1) having a CV value of 8% or less .
(3) The conductive multifilament according to (1) or (2), wherein the rate of change in CV value of electrical resistance between 25°C and 170°C is 15% or less.
(4) The conductive multifilament according to any one of (1) to (3), having an elongation of 40 to 70%.
(5) A method for producing the conductive multifilament according to any one of (1) to (4), comprising the following steps (a) to (c) in this order.
(a) A polyamide resin containing 15 to 35% by mass of conductive particles and having a relative viscosity of 2.0 to 2.9 is spun at a spinning temperature of (melting point of polyamide resin +15) to (melting point of polyamide resin +50). ) C. and a spinning speed of 500 to 1500 m/min to obtain an undrawn multifilament. (b) The undrawn multifilament is subjected to a stretching treatment at a draw ratio of 2.0 to 3.0 times and a temperature of 35° C. or lower. A step (c) of preheating the drawn multifilament at 120°C or higher and then heat-treating it at 160 to 200°C (6) Any of (1) to (4) to obtain a multifilament. A woven or knitted fabric containing conductive multifilaments.
(7) A brush containing the conductive multifilament according to any one of (1) to (4).

The conductive multifilament of the present invention not only has excellent conductivity, but also has a low dry heat shrinkage rate after heat treatment at high temperatures and suppresses thread unevenness, so it has excellent conductivity even under high temperature environments. As a result, uniform conductivity can be achieved. Therefore, it can be suitably used in textile products that require stable and uniform conductivity, such as clothing and industrial material applications (brushes for precision instruments, etc.).

The present invention will be explained in detail below.
(Conductive multifilament)
The conductive multifilament of the present invention is a multifilament composed of single fibers made of a thermoplastic resin containing conductive particles in a proportion of 15 to 35% by mass.

Examples of the thermoplastic resin include polyamide resin, polyester resin, polyolefin resin, and the like. Among these, polyamide resin is preferred from the viewpoint of mechanical properties, strength, etc. Examples of the polyamide resin include nylon 6, nylon 66, nylon 69, nylon 46, nylon 610, nylon 12, etc. alone, copolymerized, or blended (mixed), but these are preferred because they allow easy kneading of conductive particles. Nylon 6 is preferred because it has a high melting point and excellent spinnability.

Examples of the conductive particles include particles made of carbon black, metal powder (silver, nickel, copper, iron, or alloys thereof, etc.), and metal compounds such as copper sulfide, copper iodide, zinc sulfide, and cadmium sulfide. . Further, conductive particles may be made by adding a small amount of antimony oxide to tin oxide or adding a small amount of aluminum oxide to zinc oxide. Furthermore, it is also possible to use conductive particles obtained by coating the surface of titanium oxide with tin oxide and mixing and firing antimony oxide. Among these, carbon black is preferred from the viewpoints of versatility, conductivity, ease of handling, and the like.

The particle size of the conductive particles is not particularly limited, but the average particle size is preferably 200 nm or less, more preferably 100 nm or less. When the average particle diameter is 200 nm or less, the conductive particles will have good dispersibility in the thermoplastic resin, and properties such as conductivity and strength and elongation will be better. The lower limit of the average particle diameter of the conductive particles is not particularly limited, but is preferably 10 nm due to concerns about aggregation.

In the single fiber constituting the conductive multifilament of the present invention, the content of conductive particles in the thermoplastic resin is 15 to 35% by mass, preferably 20 to 30% by mass. If the content is less than 15% by mass, the conductivity will be poor, while if it exceeds 35% by mass, the conductive particles will not be well dispersed in the thermoplastic resin, making it impossible to suppress thread unevenness. As a result, the CV value of the electrical resistance value becomes large, and the variation in conductivity becomes large, resulting in a problem that uniform conductivity cannot be obtained.

The conductive multifilament of the present invention needs to have a dry heat shrinkage rate of 3.0% or less at 170°C, preferably 2.6% or less, and preferably 2.0% or less. More preferably, it is 1.5% or less. Generally, the shrinkage rate of long fibers is often evaluated using the boiling water shrinkage rate. However, when the conductive multifilament of the present invention is used in, for example, electronic equipment, factory uniforms, etc., it may be exposed to instantaneous high temperatures in a dry state due to heat generated by the equipment. Alternatively, when storing the conductive multifilament of the present invention for a long period of time in a high temperature environment, subjecting it to various processing, or ironing a woven or knitted fabric containing the conductive multifilament of the present invention, do not expose it to high temperature for a long time. You may be exposed. The present inventors discovered that when conventional conductive multifilaments are used in high-temperature environments, they are deformed by heat and the uniformity of conductivity is lost. It was discovered that the The inventors of the present invention were able to solve the above problem by setting the dry heat shrinkage rate after heat treatment at 170°C to 3.0% or less, and the uniformity of conductivity was achieved even in a high-temperature environment. It has been found that stable conductivity can be obtained. A method for making the dry heat shrinkage rate after heat treatment at 170° C. 3.0% or less will be explained in detail in the manufacturing method described below.

The conductive multifilament of the present invention has thread unevenness of 3.0% or less as determined by the following formula.
Thread spots [%] = (|X-Xmax|/X×100 + |X-Xmin|/X×100)÷2
X: 500 m of conductive multifilament is cut into 50 pieces of 10 m each, and the average fineness of these 50 pieces is measured. Fineness Xmin: Cut 500m of conductive multifilament into 50 pieces of 10m each, and find the smallest fineness among these 50 pieces.

Conventionally, various cross-sectional shapes of fibers have been studied in order to improve conductivity and variation in conductivity. However, although it is possible to suppress variations in conductivity to a certain level using methods that control the cross-sectional shape of the fibers, it has been difficult to suppress variations resulting from unevenness of the fibers themselves in the length direction. . Therefore, by using the manufacturing method described below, it is possible to suppress unevenness in the longitudinal direction of the fibers to 3.0% or less, and it is possible to suppress variations in conductivity in the longitudinal direction of the fibers. I found out what happened. When the yarn unevenness exceeds 3.0%, the variation in electrical resistance value in the length direction of the fibers becomes large, resulting in non-uniform conductivity. Furthermore, since there are locally thinner areas, this can lead to yarn breakage during stretching. In particular, the yarn unevenness is preferably 2.5% or less, more preferably 2.0% or less.

The conductive multifilament of the present invention has an electrical resistance value of 10 ¹² Ω/cm or less at 25°C and 170°C, preferably 10 ¹¹ Ω/cm or less, and preferably 10 ¹⁰ Ω/cm or less. It is more preferable. The lower limit of the electrical resistance value is, for example, 10 ³ Ω/cm, although it is not particularly limited.
The electrical resistance value is calculated as follows using the AATCC76 method.
First, for the electrical resistance value at 25° C., a conductive multifilament placed in an atmosphere of 25° C. and 50% humidity for 15 minutes is used. For the electrical resistance value at 170° C., a conductive multifilament placed (heat treated) in an atmosphere of 170° C. and 50% humidity for 15 minutes is used. These conductive multifilaments are cut into pieces of about 15 cm to collect 10 samples. Apply keratin cream to both ends of this sample, connect this surface part to a metal terminal, apply a DC current of 50V at a sample measurement length of 10 cm to measure the current value, and use the following formula to determine the electrical resistance of the 10 samples. are measured and the average value calculated is the electrical resistance value.
Electrical resistance value (Ω/cm) = E/(I x L)
E: Voltage (V)
I: Measurement current (A)
L: Measurement length (cm)

The conductive multifilament of the present invention has the above-mentioned physical properties and suppresses variations in conductivity, so that the rate of change in electrical resistance value in the length direction of the fiber at 25°C (CV value) will be less than 5%. Among these, it is preferably 4.5% or less, more preferably 4.0% or less, and even more preferably 3.2% or less. That is, the CV value of the electrical resistance value indicates the variation in conductivity, and by setting this value to 5% or less, a conductive multifilament with suppressed variation in conductivity can be obtained.

In addition, the conductive multifilament of the present invention has the effect that, as mentioned above, the dry heat shrinkage rate at 170°C is 3.0% or less, and at the same time, variations in conductivity are suppressed even in a high temperature environment of 170°C. play. In other words, the variation rate (CV value) of the electric resistance value in the length direction of the fiber at 170° C. is 5.5% or less. Among these, it is preferably 5.0% or less, more preferably 4.5% or less, and even more preferably 4.0% or less.

The CV value of the electrical resistance value is calculated according to the following formula.
CV value (%) of electrical resistance value = (V/W) x 100
W: Electrical resistance value (Ω/cm)
V: Square root of unbiased variance of electrical resistance values. Unbiased variance is calculated by calculating the difference between the electrical resistance values and the average value of the electrical resistance values of all samples measured at 25°C and 170°C as described above. The sum of the values obtained by squaring is divided by (number of test pieces - 1) and the obtained value is adopted.

The rate of change in the CV value of electrical resistance values at 25°C and 170°C, calculated by the following formula, is preferably 15% or less, more preferably 10% or less, and 8% or less. is more preferable, and particularly preferably 5% or less.
The rate of change in the CV value of the electrical resistance value between 25° C. and 170° C. is calculated using the following formula.
Change rate (%) of CV value of electrical resistance value between 25°C and 170°C = (|a-b|÷a)×100
a: CV value of electrical resistance value at 25°C b: CV value of electrical resistance value after heat treatment at 170°C for 15 minutes In order to keep the CV value of electrical resistance value at 25°C and 170°C within the above range, as described below. This is made possible by a manufacturing method that does this.

The conductive multifilament of the present invention preferably has a melt viscosity (hereinafter sometimes simply referred to as "melt viscosity") of 1200 to 2200 dPa·s at a shear rate of 1000/sec when melted at 245°C. , more preferably 1500 to 2000 dPa·s. If the melt viscosity is less than 1200 dPa・s, the orientation of the polymer is not sufficiently promoted, and the structure of the conductive particles existing in the amorphous region deteriorates and becomes non-uniform, resulting in poor conductivity. There is. If it exceeds 2,200 dPa·s, the thickness of the fibers in the longitudinal direction is not stable, which may result in poor thread unevenness and large variations in conductivity.
The method for measuring melt viscosity at a shear rate of 1000/sec when melted at 245°C will be described later in Examples.

In order to make the melt viscosity of the conductive multifilament at 245° C. within the above range, for example, the content of the conductive particles should be within the above range, and then, for example, the relative viscosity of the thermoplastic resin should be set in a preferable range. , or the spinning temperature can be set within a specific range. The relative viscosity in the present invention is measured using 96% by mass sulfuric acid as a solvent at a concentration of 1 g/dl and a temperature of 25°C. In the present invention, the relative viscosity of the thermoplastic resin is preferably 2.0 to 2.9, more preferably 2.3 to 2.7. Thereby, the melt viscosity of the conductive multifilament at 245° C. can be kept in a preferable range while keeping the content of the conductive particles in a preferable range.

The elongation of the conductive multifilament of the present invention is preferably 40 to 70%, more preferably 45 to 65%. By setting it within this range, destruction of the structure (connection of conductive particles) is further suppressed, and better and more uniform conductivity can be obtained. That is, if the elongation is less than 40%, the distortion of the fibers becomes large, the structure may be destroyed, and the conductivity may vary. If the elongation exceeds 70%, the strength will be poor, and deformation due to external force will easily occur, and variations in conductivity in the length direction of the fibers may occur.

As a method for making the elongation of the conductive multifilament of the present invention within the above range, for example, in the manufacturing method described below, a method of drawing at a magnification within a specific range may be mentioned.

In the conductive multifilament of the present invention, the CV value of fineness is preferably 8% or less, more preferably 5% or less, and even more preferably 4.5% or less. The CV value of fineness is an index of variation among single fibers. If the CV value of fineness exceeds 8%, it may not be possible to suppress variations in conductivity in the length direction of the fibers.

As a method for setting the CV value of the fineness of the conductive multifilament of the present invention within the above range, it is possible to set preferable spinning conditions or drawing conditions in the manufacturing method as described below.

The conductive multifilament of the present invention contains stabilizing agents such as waxes, polyalkylene oxides, various surfactants, dispersants such as organic electrolytes, antioxidants, and ultraviolet absorbers, to the extent that the effects of the present invention are not impaired. A matting agent, a coloring agent, a pigment, a fluidity improver, and other additives may be included depending on the purpose.

The conductive multifilament of the present invention may be subjected to known processing such as false twisting. Alternatively, it may be used in combination with other fibers by interlace processing, taslan processing, etc. Furthermore, the fineness and number of filaments of the conductive multifilament of the present invention can be appropriately set depending on the application and the like.

(Method for manufacturing conductive multifilament)
Next, the method for manufacturing a conductive multifilament of the present invention includes the following steps (a) to (c) in this order.
(a) A thermoplastic resin containing 15 to 35% by mass of conductive particles and a relative viscosity of 2.0 to 2.9 is spun at a spinning temperature (melting point of thermoplastic resin + 15) to (thermoplastic resin melt spinning at +50)°C and a spinning speed of 500 to 1500 m/min to obtain an undrawn multifilament. Step (c) of preheating the drawn multifilament at 120°C or higher and then heat-treating it at 160 to 200°C to obtain a multifilament.

The above step (a) (spinning step) will be described below.
First, as a method for obtaining a thermoplastic resin containing conductive particles at a ratio of 15 to 35% by mass and having a relative viscosity of 2.0 to 2.9, conductive particles are added during the polymerization stage of the thermoplastic resin. There is a method in which conductive particles are added to a thermoplastic resin in a subsequent step and melt-kneaded. Among these, since some polymers are difficult to add at the polymerization stage, a method of melt-kneading in a subsequent step is preferred. Note that the relative viscosity of the thermoplastic resin is preferably 2.3 to 2.7. The relative viscosity of the thermoplastic resin can be adjusted by appropriately changing the polymerization temperature and time. If the relative viscosity of the thermoplastic resin is less than 2.0, the resulting conductive multifilament may have poor conductivity. On the other hand, if the relative viscosity of the thermoplastic resin exceeds 2.9, the resulting conductive multifilament will be inferior in CV value of fineness or yarn unevenness, resulting in poor variation in conductivity.

Using the thermoplastic resin obtained in this way, it is processed by drying and other processes as necessary to form chips, which are kneaded and melted using an ordinary melt spinning device, for example, an extruder, and then extruded from a spinneret. Melt spinning is performed to obtain an undrawn multifilament. The method of melt spinning is not particularly limited and can be carried out by a conventional method.

The spinning temperature is (melting point +15) to (melting point +50)°C, preferably (melting point +20) to (melting point +40)°C, relative to the melting point of the thermoplastic resin used. When the spinning temperature exceeds (melting point + 50°C), thermal decomposition of the thermoplastic resin is likely to be accelerated, yarn unevenness becomes worse, and variations in conductivity cannot be suppressed. Moreover, if the spinning temperature is less than (melting point +15)°C, undissolved substances tend to remain and uniform kneading cannot be achieved. The spun filament (undrawn multifilament) is cooled, for example, by cooling air, and further wound up at a take-up speed of 500 to 1500 m/min. That is, the spinning speed is 500 to 1500 m/min. When the spinning speed is lower than 500 m/min, solidification is not promoted and fiber formation becomes unstable, yarn unevenness worsens, and variations in conductivity cannot be suppressed. On the other hand, if the spinning speed is excessively high, exceeding 1500 m/min, spinning operability will decrease. The spinning speed is preferably 600 to 1400 m/min, more preferably 700 to 1300 m/min.

The above step (b) (stretching step) will be described below. In step (b), the undrawn multifilament obtained in step (a) is subjected to a drawing treatment. In the conductive multifilament of the present invention, it is important to perform the stretching treatment at a temperature of 35° C. or lower without heating with a heating roller or the like. In other words, if the stretching process is performed at a temperature exceeding 35°C, the molecular orientation of the conductive multifilament cannot be sufficiently promoted, resulting in a high dry heat shrinkage rate and poor dimensional stability. It is not possible to suppress variations in conductivity.

In the above step (b), the lower limit of the temperature during stretching is not particularly limited, but is preferably, for example, 20°C.

In the above step (b), the stretching ratio is 2.0 to 3.0 times, preferably 2.3 to 2.7 times. When the stretching ratio is within the above range, the elongation of the conductive multifilament of the present invention can be within the range of the present invention, and variations in conductivity can be suppressed. That is, if the stretching ratio is less than 2.0 times, the elongation of the resulting conductive multifilament becomes excessively high, uneven structure formation occurs in the fiber direction, and variations in conductivity are not suppressed. On the other hand, if the stretching ratio exceeds 3.0 times, the elongation of the resulting conductive multifilament will be excessively low, the structure inside the fiber will become unstable, yarn unevenness will not be sufficiently suppressed, and the conductive multifilament will become unstable. Variations are not suppressed.

The stretching ratio in the above step (b) satisfies the above range (2.0 to 3.0 times, preferably 2.3 to 2.7 times), and from the viewpoint of operability, for example, the maximum stretching ratio ( It is more preferably 80% or less, even more preferably 75% or less, particularly preferably 70% or less of the magnification at which the undrawn multifilament is cut by stretching. The maximum stretching ratio refers to the point at which the unstretched multifilament obtained in step (a) is cut when stretched. Specifically, if the obtained undrawn multifilament is subjected to drawing, the drawing ratio is gradually increased, and it breaks when the drawing ratio reaches 3.0 times, then the undrawn multifilament is The maximum stretching ratio is 3.0 times, and the stretching ratio as a production condition is preferably 80% or less (that is, 2.4 times or less).

The above step (c) (heat treatment step) will be described below. In step (c), after preheating to 120°C or higher (hereinafter sometimes referred to as "first heat treatment"), heat treatment is performed at 160 to 200°C (hereinafter referred to as "second heat treatment"). There is). The first heat treatment temperature is preferably 130°C or higher, and the second heat treatment temperature is preferably 170 to 190°C.

By performing such two-step heat treatment, it is possible to apply an appropriate amount of heat to the yarn, reduce the dry heat shrinkage rate, and suppress variations in conductivity in a high-temperature environment. Furthermore, by closely linking (contacting) the conductive particles in the single fibers constituting the multifilament, the conductivity can be uniformly improved. If only one stage of heat treatment is performed, or if the heat treatment temperatures of the first and second heat treatments are outside the above range, sufficient heat cannot be applied to the yarn and the dry heat shrinkage rate will be reduced. Therefore, it is not possible to suppress variations in conductivity in a high-temperature environment.

If the temperature in the first heat treatment is less than 120°C, it will not be possible to apply a sufficient amount of heat to the yarn, resulting in a high dry heat shrinkage rate, which will suppress variations in conductivity in a high-temperature environment. I can't. On the other hand, the upper limit of the temperature in the first heat treatment is not particularly limited, but from the viewpoint of the amount of heat given to the yarn and operability, it is preferably lower than the second heat treatment temperature.

If the temperature in the second heat treatment is less than 160°C, a sufficient amount of heat cannot be applied to the yarn, so crystallization of the yarn cannot be promoted, resulting in a high dry heat shrinkage rate. Therefore, it is not possible to suppress variations in conductivity in a high-temperature environment. On the other hand, if the temperature exceeds 200°C, pseudo-fusion tends to occur, making it difficult to roll up.

In the first heat treatment and the second heat treatment, for example, a heat roller, a heat plate, etc. can be used.

The conductive multifilament of the present invention is suitably used in textile products that require stable and uniform conductivity, such as industrial material applications (brushes for precision instruments, etc.).

The woven or knitted fabric of the present invention contains the conductive multifilament of the present invention. In the woven or knitted fabric of the present invention, the mixing ratio of the conductive multifilament is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. The woven or knitted fabric of the present invention can be used, for example, in clothing applications (work clothes, dustproof clothing, clean room clothing, etc.) or industrial material applications (smartphone gloves, smart textiles, charging brushes used in electronic devices, etc.). In particular, the conductive multifilament of the present invention has a reduced dry heat shrinkage rate at high temperatures, thereby suppressing variations in conductivity at high temperatures, and is therefore particularly preferable for applications employed in high-temperature environments.

When the woven or knitted fabric of the present invention is a woven fabric, specific examples of its texture include plain weave, twill weave, satin weave, or twine weave. The fabric density is not particularly limited, but the warp density is preferably 50 to 250 threads/2.54 cm, and the weft density is preferably 50 to 250 threads/2.54 cm.

When the woven or knitted fabric of the present invention is a knitted fabric, specific examples of its texture include Kanoko, milling, and smooth. The knitted fabric density is not particularly limited, but examples include 20 to 150 courses/inch and 20 to 150 wales/inch.

Next, the present invention will be specifically explained with reference to examples, but is not limited to the following examples. In addition, various characteristic values and evaluations in Examples were performed as follows.

(1) Relative viscosity Measured using 96% by mass sulfuric acid as a solvent at a concentration of 1 g/dl and a temperature of 25°C.

(2) Dry heat shrinkage rate The fiber length of the conductive multifilament was measured under no load, then heat treated at 170° C. for 15 minutes, and the fiber length after the heat treatment was similarly measured. The dry heat shrinkage rate was calculated from the fiber length before heat treatment (A) and the fiber length after heat treatment (B) using the following formula.
Dry heat shrinkage rate (%) = [(AB)/A] x 100

(3) Thread unevenness Divide 500 m of conductive multifilament into 50 pieces of 10 m each, measure the fineness of each by weight measurement, and set the average value of the fineness of the 50 pieces as X, the maximum value as Xmax, and the minimum value as Xmin, as follows. It was calculated using the formula.
Thread spot (%) = (|X-Xmax|/X + |X-Xmin|/X|)÷2

(4) CV value of fineness A photograph of the fiber cross section was taken using a digital microscope VHX-600 manufactured by Keyence Corporation, C and D were calculated from the cross-sectional area of each single fiber, and the CV value was determined based on the following formula. .
Fineness CV value (%) = (C/D) x 100
C: Parallel root of unbiased dispersion of all single fiber cross-sectional areas of the conductive multifilament D: Average value of all single fiber cross-sectional areas of the conductive multifilament The unbiased dispersion of single fiber cross-sectional areas was determined as follows. . That is, for all the test pieces, the difference between the single fiber cross-sectional area and the average value of the single fiber cross-sectional area was determined. The sum of the values obtained by squaring these differences was divided by (the number of test pieces - 1), and the obtained value was taken as unbiased variance.

(5) Elongation Measured based on JIS L1013 8.5.1 (standard time test). The measurement was performed using "TENSILON RTC-1210" manufactured by ORIENTEC under the conditions of a grip interval of 25 cm and a tensile speed of 30 cm/min.

(6) Electrical resistance value at 25°C and 170°C Calculated using AATCC76 method as follows.
First, the electrical resistance value at 25° C. was determined by using a conductive multifilament placed in an atmosphere at 25° C. and 50% humidity for 15 minutes. The electrical resistance value at 170° C. was determined by using a conductive multifilament placed (heat treated) in an atmosphere of 170° C. and 50% humidity for 15 minutes. These conductive multifilaments are cut into pieces of about 15 cm to collect 10 samples. Apply keratin cream to both ends of this sample, connect this surface part to a metal terminal, apply a DC current of 50V at a sample measurement length of 10 cm to measure the current value, and use the following formula to determine the electrical resistance of the 10 samples. were measured, and the calculated average value was taken as the electrical resistance value.
Electrical resistance value (Ω/cm) = E/(I x L)
E: Voltage (V)
I: Measurement current (A)
L: Measurement length (cm)

(7) CV value of electrical resistance value Calculated according to the following formula.
CV value (%) of electrical resistance value = (V/W) x 100
W: Electrical resistance value (Ω/cm)
V: Square root of unbiased variance of electrical resistance values. Unbiased variance is calculated by calculating the difference between the electrical resistance values and the average value of the electrical resistance values of all samples measured at 25°C and 170°C as described above. The sum of the values obtained by squaring was divided by (number of test pieces - 1), and the obtained value was adopted.

(8) Rate of change in CV value of electrical resistance between 25°C and 170°C Calculated using the following formula.
Change rate (%) of CV value of electrical resistance value between 25°C and 170°C = (|a-b|÷a)×100
a: CV value of electrical resistance value at 25°C b: CV value of electrical resistance value after heat treatment at 170°C for 15 minutes

(9) Melt viscosity at a shear rate of 1000/sec when melted at 245°C Conductive multifilament was melted at 245°C using a Shimadzu flow tester (CFT-500) and the shear rate was 1000/sec ^- The viscosity at ¹ was defined as the melt viscosity.

Example 1
Using polyamide resin (nylon 6, relative viscosity 2.5, melting point 225°C) as a thermoplastic resin, nylon 6 containing 24.1% by mass of carbon black as conductive particles is supplied to a normal spinning device. Then, melt spinning was performed at a spinning temperature of 245° C. using a spinneret having 96 spinning holes with a hole diameter of 0.25 mm. The spun yarn was cooled and wound at a speed of 800 m/min while oiling to obtain an undrawn yarn of 535 dtex/96 f (maximum draw ratio: 3.65 times). This undrawn yarn was stretched 2.41 times using a roller at 30°C, preheated using a heated roller at 142°C (first heat treatment), and then heat treated on a heat plate at 180°C (second heat treatment). After performing heat treatment), it was wound up to obtain a conductive multifilament of 220 dtex/96 f, which was subjected to evaluation.

Examples 2 to 5, Comparative Examples 1 to 4
A conductive multifilament was obtained in the same manner as in Example 1, except that the stretching ratio was changed as shown in Table 1 according to the relative viscosity of the polyamide resin, the content of carbon black, or the maximum stretching ratio of the undrawn yarn. Ta.

Example 6, Comparative Examples 5-6
A conductive multifilament was obtained in the same manner as in Example 1, except that the spinning speed was changed as shown in Table 1.

Comparative example 7
A conductive multifilament was obtained in the same manner as in Example 1, except that the temperature conditions in the stretching process were changed as shown in Table 1.

Examples 7-9, Comparative Examples 8-9
A conductive multifilament was obtained in the same manner as in Example 1, except that the first heat treatment temperature and the second heat treatment temperature were changed as shown in Table 1.

Comparative examples 10-11
A conductive multifilament was obtained in the same manner as in Example 1, except that the first heat treatment was not performed, and the film was stretched at the stretching temperature listed in Table 1 and simultaneously subjected to tension heat treatment using a heat plate.

Comparative examples 12-13
A conductive multifilament was obtained in the same manner as in Example 1, except that the stretching ratio in the stretching step was changed as shown in Table 1.
The conditions and evaluation results of Examples and Comparative Examples are summarized in Tables 1 and 2.

As is clear from Table 2, the conductive multifilaments of the present invention obtained in Examples 1 to 9 had a small dry heat shrinkage rate and suppressed thread unevenness, so the CV value of the electrical resistance value ( The variation in conductivity was small, and uniform conductivity was achieved even in high-temperature environments.

The multifilament obtained in Comparative Example 1 had an excessive carbon black content, which made the ejection from the nozzle unstable, and the CV value of fineness and yarn unevenness were poor, resulting in poor conductivity. The results showed poor variation.

The multifilament obtained in Comparative Example 2 had poor conductivity because the content of carbon black in the polyamide resin was too small.

The multifilament obtained in Comparative Example 3 had a low melt viscosity and poor conductivity because the relative viscosity of the polyamide resin was too low.

The multifilament obtained in Comparative Example 4 had a high melt viscosity because the relative viscosity of the polyamide resin was too high, and the CV value of fineness and yarn unevenness were poor, resulting in poor conductivity variation. It became.

In the multifilament obtained in Comparative Example 5, because the spinning speed was too slow, solidification was not promoted and fiber formation became unstable, resulting in poor yarn unevenness and poor conductivity variation. .

In the multifilament obtained in Comparative Example 6, since the spinning speed was too high, the yarn discharged from the spinneret caused draft breakage, and winding was impossible.

In the multifilament obtained in Comparative Example 7, the temperature during stretching was 80°C, which was higher than the range of the present invention, so the orientation was not promoted and the dry heat shrinkage rate was high, so it could not be used in a high-temperature environment. The variation in conductivity was poor.

In the multifilament obtained in Comparative Example 8, since the first heat treatment temperature was too low, it was not possible to impart a sufficient amount of heat to the yarn, resulting in a high dry heat shrinkage rate. The variation in conductivity was poor.

The multifilament obtained in Comparative Example 9 was unable to impart a sufficient amount of heat to the yarn because the second heat treatment temperature was too low, resulting in a high dry heat shrinkage rate. The variation in conductivity was poor.

The multifilament obtained in Comparative Example 10 was not subjected to the first heat treatment, so it was not possible to apply a sufficient amount of heat to the yarn, and the multifilament obtained in Comparative Example 10 was not subjected to the first heat treatment, so it was not possible to apply a sufficient amount of heat to the yarn. As a result of the higher shrinkage rate, the conductivity was less uniform under high-temperature environments.

In the multifilament obtained in Comparative Example 11, the orientation was not promoted because the temperature during stretching was too high, and compared to Comparative Example 10, the dry heat shrinkage rate was even higher, and the conductivity in a high temperature environment was lowered. This resulted in poor gender disparity.

In the multifilament obtained in Comparative Example 12, the stretching ratio during stretching was too low, resulting in high elongation, uneven structure formation in the fiber direction, and poor variation in conductivity. .

In the multifilament obtained in Comparative Example 13, the stretching ratio during stretching was too high, so the elongation was low, the structure inside the fiber was unstable, yarn unevenness was not sufficiently suppressed, and the conductivity was poor. There was a bad variation in the results.

Claims (7)

A conductive multifilament composed of single fibers made of polyamide resin containing conductive particles in a proportion of 15 to 35% by mass, and characterized in that it satisfies the following (I) to (V) at the same time: filament.
(I) Dry heat shrinkage rate at 170°C is 3.0% or less (II) Electrical resistance value at 25°C and 170°C is 10 ¹² Ω/cm or less (III) Thread unevenness is 3.0% or less (IV) 25°C The CV value of the electrical resistance value in the longitudinal direction of the fiber at 170°C is 5.0% or less (V) The CV value of the electrical resistance value in the longitudinal direction of the fiber at 170°C is 5.5% or less The conductive multifilament according to claim 1, having a CV value of fineness of 8% or less . The conductive multifilament according to claim 1 or 2, wherein the rate of change in the CV value of the electrical resistance value between 25°C and 170°C is 15% or less. The conductive multifilament according to any one of claims 1 to 3, having an elongation of 40 to 70%. A method for manufacturing the conductive multifilament according to any one of claims 1 to 4, comprising the following steps (a) to (c) in this order.
(a) A polyamide resin containing 15 to 35% by mass of conductive particles and having a relative viscosity of 2.0 to 2.9 is spun at a spinning temperature of (melting point of polyamide resin +15) to (melting point of polyamide resin +50). ) C. and a spinning speed of 500 to 1500 m/min to obtain an undrawn multifilament. (b) The undrawn multifilament is subjected to a stretching treatment at a draw ratio of 2.0 to 3.0 times and a temperature of 35° C. or lower. to obtain a multifilament (c) A step of preheating the drawn multifilament at 120°C or higher and then heat treating it at 160 to 200°C. A woven or knitted fabric comprising the conductive multifilament according to any one of claims 1 to 4. A brush comprising the conductive multifilament according to any one of claims 1 to 4.